Circuits, in particular integrated circuits (IC), such as microprocessors, flip-flops, latches, memory cells, etc., experience voltage and/or current anomalies over the circuit lifetime due to the operating environment and/or the design of the circuits. The phrase ‘voltage anomaly’ and the phrase ‘current anomaly’ is referred to herein, and used interchangeably with, the term ‘fault event’. Examples of a fault event include a Single-Event Upset (SEU), a fault due to accelerated ageing, and supply voltage non-idealities such as supply droops and/or ground bounce. Fault events may affect the reliable functioning of a circuit.
Reliability of a circuit becomes paramount in safety-critical applications, such as, automotive applications, medical applications, military applications and aerospace applications. The circuits used in the safety-critical applications may be subjected to extreme operating conditions, such as, extreme temperatures, radiation effects, and the like. Exposure to such extreme operating conditions increases susceptibility to reliability issues such as accelerated ageing of transistors, and/or an increased sensitivity to SEUs. Accelerated ageing is a phenomenon where a circuit begins to wear out rapidly in comparison with an expected life time of the circuit, leading to gradual slow-down in switching speeds that adversely impact circuit-timing assumptions. SEU may be an unwanted change in state in state-holding elements, or a transient voltage pulse at sensitive nodes in the ICs, such as, processors. Other fault events such as supply-voltage droops and ground bounce occur due to interactions of the IC with the associated circuitry that delivers power to the transistors in the IC. Such reliability and functional issues may cause a system malfunction which the circuits are a part of. The system malfunction may disrupt operation of the system, in particularly, safety-critical applications, leading to a loss of number of research hours, manpower, lives and/or investments. Identifying occurrences of the fault events and identifying the circuits exhibiting the fault events may help to understand the reliability and functionality issues of the circuits.